NAME

SYNOPSIS

DESCRIPTION

Halt notes that the system is being brought down in the file
/var/log/wtmp, and then either tells the kernel to halt, reboot or
power-off the system.

If halt or reboot is called when the system is
not in runlevel 0 or 6, in other words when it's running
normally, shutdown will be invoked instead (with the -h
or -r flag). For more info see the shutdown(8)
manpage.

The rest of this manpage describes the behaviour in runlevels 0
and 6, that is when the systems shutdown scripts are being run.

OPTIONS

-n

Don't sync before reboot or halt. Note that the kernel and storage
drivers may still sync.

-w

Don't actually reboot or halt but only write the wtmp record
(in the /var/log/wtmp file).

Put all hard drives on the system in stand-by mode just before halt or power-off.

-p

When halting the system, switch off the power. This is the default when halt is
called as poweroff.

-k

Try to reboot using kexec, if kernel supports it.

DIAGNOSTICS

If you're not the superuser, you will get the message `must be superuser'.

NOTES

Under older sysvinit releases , reboot and halt should
never be called directly. From release 2.74 on halt and reboot
invoke shutdown(8) if the system is not in runlevel 0 or 6. This
means that if halt or reboot cannot find out the current
runlevel (for example, when /var/run/utmp hasn't been initialized
correctly) shutdown will be called, which might not be what you want.
Use the -f flag if you want to do a hard halt or reboot.

The -h flag puts all hard disks in standby mode just before halt
or power-off. Right now this is only implemented for IDE drives. A side
effect of putting the drive in stand-by mode is that the write cache
on the disk is flushed. This is important for IDE drives, since the
kernel doesn't flush the write cache itself before power-off.

The halt program uses /proc/ide/hd* to find all IDE disk devices,
which means that /proc needs to be mounted when halt or
poweroff is called or the -h switch will do nothing.